Stentless support structure

ABSTRACT

A stentless support structure capable of being at least partly assembled in situ. The support structure comprises a braided tube that is very flexible and, when elongated, becomes very long and very small in diameter, thereby being capable of placement within a small diameter catheter. The support structure is preferably constructed of one or more thin strands of a super-elastic or shape memory material such as Nitinol. When released from the catheter, the support structure folds itself into a longitudinally compact configuration. The support structure thus gains significant strength as the number of folds increase. This radial strength obviates the need for a support stent. The support structure may include attachment points for a prosthetic valve.

CROSS-REFERENCE TO RELATED DOCUMENTS

This application is related to and claims priority benefit of U.S.Provisional Patent Application Ser. No. 60/685,349, filed May 27, 2005,entitled Stentless Support Structure, by Wilson et al. and U.S.Provisional Patent Application Ser. No. 60/709,595, filed Aug. 18, 2005,entitled Stentless Support Structure by Wilson et al. These applicationsare also hereby incorporated by reference herein. This application alsoincorporates by reference U.S. patent application Ser. No. ______entitled Intravascular Cuff filed by Applicant on even date herewith andU.S. Provisional Patent Application Ser. No. 60/685,433, filed May 27,2005, entitled Intravascular Cuff

BACKGROUND OF THE INVENTION

There has been a significant movement toward developing and performingcardiovascular surgeries using a percutaneous approach. Through the useof one or more catheters that are introduced through, for example, thefemoral artery, tools and devices can be delivered to a desired area inthe cardiovascular system to perform many number of complicatedprocedures that normally otherwise require an invasive surgicalprocedure. Such approaches greatly reduce the trauma endured by thepatient and can significantly reduce recovery periods. The percutaneousapproach is particularly attractive as an alternative to performingopen-heart surgery.

Valve replacement surgery provides one example of an area wherepercutaneous solutions are being developed. A number of diseases resultin a thickening, and subsequent immobility or reduced mobility, of heartvalve leaflets. Such immobility also may lead to a narrowing, orstenosis, of the passageway through the valve. The increased resistanceto blood flow that a stenosed valve presents can eventually lead toheart failure and ultimately death.

Treating valve stenosis or regurgitation has heretofore involvedcomplete removal of the existing native valve through an open-heartprocedure followed by the implantation of a prosthetic valve. Naturally,this is a heavily invasive procedure and inflicts great trauma on thebody leading usually to great discomfort and considerable recovery time.It is also a sophisticated procedure that requires great expertise andtalent to perform.

Historically, such valve replacement surgery has been performed usingtraditional open-heart surgery where the chest is opened, the heartstopped, the patient placed on cardiopulmonary bypass, the native valveexcised and the replacement valve attached. A proposed percutaneousvalve replacement alternative method on the other hand, is disclosed inU.S. Pat. No. 6,168,614 (the entire contents of which are herebyincorporated by reference) issued to Andersen et al. In this patent, theprosthetic valve is mounted on a stent that is collapsed to a size thatfits within a catheter. The catheter is then inserted into the patient'svasculature and moved so as to position the collapsed stent at thelocation of the native valve. A deployment mechanism is activated thatexpands the stent containing the replacement valve against the valvecusps. The expanded structure includes a stent configured to have avalve shape with valve leaflet supports begins to take on the functionof the native valve. As a result, a full valve replacement has beenachieved but at a significantly reduced physical impact to the patient.

However, this approach has decided shortcomings. One particular drawbackwith the percutaneous approach disclosed in the Andersen '614 patent isthe difficulty in preventing leakage around the perimeter of the newvalve after implantation. Since the tissue of the native valve remainswithin the lumen, there is a strong likelihood that the commissuraljunctions and fusion points of the valve tissue (as pushed apart andfixed by the stent) will make sealing around the prosthetic valvedifficult. In practice, this has often led to severe leakage of bloodaround the stent apparatus.

Other drawbacks of the Andersen '614 approach pertain to its reliance onstents as support scaffolding for the prosthetic valve. First, stentscan create emboli when they expand. Second, stents are typically noteffective at trapping the emboli they dislodge, either during or afterdeployment. Third, stents do not typically conform to the features ofthe native lumen in which they are placed, making a prosthetic valvehoused within a stent subject to paravalvular leakage. Fourth, stentsare subject to a tradeoff between strength and compressibility. Fifth,stents cannot be retrieved once deployed. Sixth, the inclusion of thevalve within the stent necessarily increases the collapsed diameter ofthe stent-valve complex and increases the caliber of the material thatmust be delivered into the vasculature.

As to the first drawback, stents usually fall into one of twocategories: self-expanding stents and expandable stents. Self-expandingstents are compressed when loaded into a catheter and expand to theiroriginal, non-compressed size when released from the catheter. These aretypically made of Nitinol. Balloon expandable stents are loaded into acatheter in a compressed but relaxed state. These are typically madefrom stainless steel or other malleable metals. A balloon is placedwithin the stent. Upon deployment, the catheter is retracted and theballoon inflated, thereby expanding the stent to a desired size. Both ofthese stent types exhibit significant force upon expansion. The force isusually strong enough to crack or pop thrombosis, thereby causing piecesof atherosclerotic plaque to dislodge and become emboli. If the stent isbeing implanted to treat a stenosed vessel, a certain degree of suchexpansion is desirable. However, if the stent is merely being implantedto displace native valves, less force may be desirable to reduce thechance of creating emboli.

As to the second drawback, if emboli are created, expanded stentsusually have members that are too spaced apart to be effective to trapany dislodged material. Often, secondary precautions must be takenincluding the use of nets and irrigation ports.

The third drawback is due to the relative inflexibility of stents.Stents typically rely on the elastic nature of the native vessel toconform around the stent. Stents used to open a restricted vessel do notrequire a seal between the vessel and the stent. However, when using astent to displace native valves and house a prosthetic valve, a sealbetween the stent and the vessel is necessary to prevent paravalvularleakage. Due to the non-conforming nature of stents, this seal is hardto achieve, especially when displacing stenosed valve leaflets.

The fourth drawback is the tradeoff between compressibility andstrength. Stents are made stronger or larger by manufacturing them withthicker members. Stronger stents are thus not as compressible as weakerstents. Most stents suitable for use in a valve are not compressibleenough to be placed in a small diameter catheter, such as a 20 Fr, 16 Fror even 14 Fr catheter. Larger delivery catheters are more difficult tomaneuver to a target area and also result in more trauma to the patient.

The fifth drawback of stents is that they are not easily retrievable.Once deployed, a stent may not be recompressed and drawn back into thecatheter for repositioning due to the non-elastic deformation (stainlesssteel) or the radial force required to maintain the stent in place(Nitinol). Thus, if a physician is unsatisfied with the deployedlocation or orientation of a stent, there is little he or she can do tocorrect the problem.

The sixth drawback listed above is that the combination of the valvewithin the stent greatly increases the size of the system required todeliver the prosthetic device. As a result, the size of the entry holeinto the vasculature is large and often precludes therapy, particularlyin children, smaller adults or patients with pre-existing vasculardisease.

It is thus an object of the present invention to address thesedrawbacks. Specifically, it is an object of the invention to provide asupport structure that expands gently, with gradual force, therebyminimizing the generation of emboli.

It is further an object of the invention to provide a support structurethat traps any emboli generated, thereby preventing the emboli fromcausing damage downstream.

It is yet another object of the invention to provide a support structurethat conforms to the features of the lumen in which it is beingdeployed, thereby preventing paravalvular leakage.

It is still another object of the invention to provide a strong supportstructure capable of being deployed from a very small diameter catheter.

It is further an object of the invention to provide a support structurethat is capable of being retracted back into a delivery catheter andredeployed therefrom.

It is another object of the invention to provide a device that isdelivered with the valve distinctly separated from the inside diameterof the final configuration of the support structure in order to reducethe amount of space required to deliver the device within thevasculature of the patient.

BRIEF SUMMARY OF THE INVENTION

The present invention accomplishes the aforementioned objects byproviding a tubular mesh support structure for a native lumen that iscapable of being delivered via a very small diameter delivery catheter.The tubular mesh is formed one or more fine strands braided togetherinto an elongate tube. The strands may be fibrous, non-fibrous,multifilament, or monofilament. The strands exhibit shape memory suchthat the elongate tube may be formed into a desired folded shape, thenstretched out into a very small diameter, elongated configuration. Thesmall diameter, elongated configuration makes a very small diameterdelivery catheter possible.

Upon deployment, the elongated tube is slowly pushed out of the deliverycatheter, where it gradually regains its folded, constructedconfiguration. The tube conforms to the internal geometries of thetarget vessel. In addition, the braid effectively traps all emboli thatmay be released from the vessel walls.

As the tube continues to be pushed from the delivery catheter, it beginsto fold in upon itself as it regains its constructed configuration. Asit folds in upon itself, the forces exerted by each layer add together,making the structure incrementally stronger. Thus, varying levels ofstrength may be achieved without changing the elongated diameter of thedevice.

Using this folded tube, the valve can be attached such that the valve orother structure (such as a filter) in its elongated configuration withinthe delivery catheter does not reside within the elongated tube, but ondeployment can be positioned in, above or below the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a preferred embodiment of the presentinvention in an elongate configuration;

FIG. 2 is a side view of a preferred embodiment of the presentinvention;

FIGS. 3-12 are a sequence of perspective views of a preferred embodimentof the present invention being deployed from a delivery catheter;

FIG. 13 is a perspective view of a preferred embodiment of the presentinvention;

FIG. 14 is a first end view of the preferred embodiment of FIG. 13;

FIG. 15 is a second end view of the preferred embodiment of FIG. 13;

FIG. 16 is a side view of a preferred embodiment of the presentinvention;

FIG. 17 is a second end view of the preferred embodiment of FIG. 16;

FIG. 18 is a first end view of the preferred embodiment of FIG. 16;

FIG. 19 is a side view of a preferred embodiment of the presentinvention;

FIG. 20 is a first end view of the preferred embodiment of FIG. 19;

FIG. 21 is a second end view of the preferred embodiment of FIG. 19;

FIG. 22 is a partial perspective view of a preferred embodiment of thepresent invention;

FIG. 23 is a partial perspective view of a preferred embodiment of thepresent invention;

FIG. 24 is a perspective view of a preferred embodiment of the presentinvention;

FIG. 25 is a side elevation of the embodiment of FIG. 24;

FIG. 26 is a second end view of the embodiment of FIG. 24;

FIGS. 27-36 are a sequence of perspective views of a preferredembodiment of the present invention being deployed from a deliverycatheter against a clear plastic tube representing a native valve;

FIG. 37 is a side elevation of a preferred embodiment of the presentinvention;

FIG. 38 is an end view of a downstream side of the embodiment of FIG.37;

FIG. 39 is an end view of an upstream side of the embodiment of FIG. 37.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the Figures and first to FIG. 1, there is shown astentless support structure 10 of the present invention in an extendedconfiguration. The valve support 10 includes a first end 12, a secondend 14 and an elongate tubular body 16 extending between the first end12 and the second end 14.

The elongate tubular body 16 is preferably formed from one or aplurality of braided strands 18. The braided strands 18 are strands of asuper-elastic or shape memory material such as Nitinol. The strands arebraided to form a tube having a central lumen 20 passing therethrough.

In one embodiment, the tubular body 16 is folded in half upon itselfsuch that the second end 14 becomes a folded end and the first end 12includes a plurality of unbraided strands. The tubular body 16 is thustwo-ply. The unbraided strands of the first end 12 are gathered andjoined together to form a plurality of gathered ends 22. The gatheredends 22 may be used as commissural points for attaching a prostheticvalve to the support structure 10. (See, e.g. FIG. 2). Alternatively, asshown in FIG. 1, the gathered ends 22 may be used as attachment pointsfor a wireform 24 defining a plurality of commissural points 26.

Notably, the commissural points 26 are positioned such that, when avalve is attached to the support structure in the extendedconfiguration, the valve is longitudinally juxtaposed with the supportstructure rather than being located within the support structure. Thisjuxtaposition allows the support structure 10 and valve to be packedinto a very small catheter without damaging the delicate valve. Thislongitudinal juxtaposition may be maintained when the support structureassumes a folded or constructed configuration (see FIG. 19 for example),or the valve may become folded within the support structure.

FIGS. 3-6 show the second end 14 emerging from the catheter 28 to exposea first layer 30. In FIG. 7, the first layer 30 is completely exposedand has assumed its constructed configuration. Notably, the first layer30 contracts longitudinally when fully deployed. Also shown in FIG. 7 isa second layer 32 beginning to emerge from the catheter 28. As thesecond layer exits the catheter, the pre-set super-elastic fold invertsthe mesh, such that a second, inner layer is formed within the firstouter layer. Alternatively, the first layer can be deployed against thewall of the vascular structure (such as an artery, vein, valve or heartmuscle). As the second layer exits the catheter, the physician can aidinversion of the mesh my advancing the deployment system. In anotherembodiment, the mesh support structure can be advanced in thevasculature such that it is deployed in a reverse direction (such asdeployment through the apex of the heart ventricle or from the venoussystem), where the mesh inversion occurs as a result of pulling orretracting the deployment system.

In FIG. 10, the second layer 32 is fully deployed and the third layer 34is fully exposed, but has not yet been inverted. Retracting the catheter28, relative to the device 10, while advancing the catheter 28 slightly,relative to the target site, causes the third layer 34 to “pop”inwardly, thereby inverting itself against an inside surface of thesecond layer 32, as seen in FIG. 11.

In FIG. 12, additional material has been ejected from the catheter 28such that the third layer 34 is fully expanded against the second layer.One skilled in the art will realize that numerous additional layers canbe achieved in this manner, and that each layer adds additional radialstrength to the resulting support structure 10.

Throughout the deployment process, the stentless support structure 10emerges from the delivery catheter 28 gradually. This characteristicalso allows the structure 10 to be pulled back into the deliverycatheter 28, in the event that it is desired to relocate the supportstructure 10. Doing so causes the support structure 10 to reacquire itsextended configuration.

Having described the mechanics of building a support structure in situ,attention can now be turned to various embodiments made possible by thepresent invention. FIGS. 13-15 show a support structure 10 having manylayers 38 and a first end 12 with numerous gathered ends 22 formed fromunbraided strands. Some of the gathered ends 22 are attached to awireform 24 having three commissural points 26. A prosthetic valve 36,either harvested or manufactured, is attached to the wireform 24. FIG.15 shows the internal lumen 20 of the support structure 10.

FIGS. 16-18 show a support structure 10 having fewer layers 38 and awireform 24 with a prosthetic valve 36 attached thereto. The first end12 (hidden), to which the wireform 24 is attached, has been preformed tofold inwardly upon deployment. Thus, the wireform 24 and prostheticvalve 36, is located in the inner lumen 20 of the support structure 10when the support structure 10 is in a constructed configuration.

FIGS. 19-21 show a support structure 10 with several layers 38 and afirst end 12 preformed to have a smaller diameter than the rest of thelayers and the second end 14, which is folded. The terminal ends of thebraided strands at the first end 12 have not been formed into gatheredends. Rather, the wireform 24 is attached to the braids. The prostheticvalve 36 is attached to the wireform 24 and has skirting tissue 40,which is placed around the outside of the end 12. The skirting tissue 40may be adhered to the first end 12.

FIG. 22 shows a stentless support structure 10 with a folded end 14,which has been folded back on itself, and a material 42 trapped betweenthe two layers of the fold. The material 42 is provided to furtherimprove the paravalvular leak prevention and embolic trappingcharacteristics of the stentless support structure 10. The material 42could consist of a non-woven material, woven or braided fabric, apolymer or other material.

FIG. 23 shows a stentless support structure 10 that includes a fiber 44that is larger than the rest of the strands comprising the supportstructure 10. Thus, FIG. 23 demonstrates that strands of different sizesmay be used in the braided support structure 10 without significantlyaffecting the minimum delivery size of the device. Different sizedstrands may be used in order to improve strength, provide stiffness,create valve attachment points, provide radiopaque markers, and thelike.

FIGS. 24-26 show a stentless support structure 10 that has a first end12 that has had the unbraided strands trimmed such that they do notextend past the first end 12 of the folded structure 10. This embodimentmay be used to create, preserve or enlarge a lumen. A prosthetic valvemay or may not be attached to this embodiment.

Turning now to FIGS. 27-36, a deployment sequence of a preferredembodiment of the stentless support structure 10 is shown whereby aclear piece of tubing 46 is used to demonstrate a targeted location of anative vessel, such as a native valve. In FIG. 27, the delivery catheter28 is advanced beyond the targeted valve 46 and the stentless support 10is starting to be ejected from the catheter 28.

In FIG. 28, enough of the stentless support 10 has been ejected that thesecond, folded end 14 has begun to curl back on itself slightly, forminga cuff 48. In FIG. 29, the cuff 48 is more visible and has assumed itsfull, deployed shape. The cuff 48 acts as a catch that a physician canuse to visually or tactilely locate the targeted valve 46 and seat thestentless support 10 thereagainst. The cuff also acts to ensure theentire native lumen through the targeted valve 46 is now being filteredby the support 10. Unlike balloon expandable stents, blood flow is notsignificantly inhibited by the deployment of the stentless supportstructure 10. Also shown in FIG. 29 is that the first layer 30 has beenfully ejected from the catheter 28, as has much of the second layer 32.The first layer 30, being very flexible prior to reinforcement bysubsequent layers, is able to conform to any shape of the targetedvessel. The second layer 32 has not yet inverted itself into the firstlayer 30.

In FIG. 30, the first layer 30 is deployed, the cuff 48 is actingagainst the valve 46, and the second layer 32 has been inverted. In FIG.31, material forming the third layer 34 is ejected from the catheter 28but the third layer 34 has not yet inverted.

In FIGS. 32-33, the catheter 28 is being advanced to allow the thirdlayer 34 to invert into the second layer 32. The angle of FIG. 32 showsthe relatively low profile created by the first and second layers 30 and32, and how little resistance to blood flow is presented by the supportstructure 10.

In FIG. 34, the first end 12 has emerged from the catheter 12, and thegathered ends 22 are showing. A wireform 24 is attached to some of thegathered ends 22 and is nearly completely deployed from the deliverycatheter 28. In FIGS. 35-36, the support structure 10 has beencompletely released from the catheter 28. FIG. 36 shows the size of thelumen 20 of the support structure 10.

FIGS. 37-39 show a preferred embodiment 100 of the present inventionincluding a mesh support structure 102, a wireform 104 and a valve 106.The support structure 102 differs slightly from support structure 10,described previously, as it is constructed from a two individual wires108. Upon completion of the braiding process, the two free ends of thewire are spliced together. As such, there are no free wire ends and thestructure can be loaded into a delivery catheter in a single-ply state(not shown). In the deployed state shown in the Figures, the supportstructure 102 is folded once to form a two-ply device.

The support structure 102 is preferably formed of a memory alloy such asNitinol. The single-wire construction allows the device to be compressedinto an extremely small catheter, such as one sized 16 Fr or smaller.Though the support structure gains rigidity by the two-ply deployedconfiguration, radial strength is a function of a several factors andcan thus be varied widely.

First, as with the other embodiments, radial strength may be increasedby incorporating more folds or layers into the deployed configuration ofthe support structure 102. The three-ply configuration shown in FIGS.37-39 is the most preferred configuration because it only has to befolded in on itself twice, making deployment less complicated.

Second, strength may be increased by using a heavier wire. Because thesupport structure 102 is made from a single-wire, and can thus be loadedinto a catheter in a single-ply configuration, a larger diameter wiremay be used while maintaining a small diameter elongated profile.Support structures 102 have been constructed according to the presentinvention using single wires having diameters between 0.005 and 0.010inches in diameter. Preferably, the diameter of the wire is between0.007 and 0.008 inches.

Third, strength may be increased by increasing the braid density. Atighter braid will result in a stronger support.

Fourth, the strength may be increased by altering the heat settingparameters. Super-elastic and shape memory alloys, such as Nitinol,attain their deployed shape within the vasculature by being heat set.The wires are held in a desired configuration and heated to apredetermined temperature for a predetermined period of time. After thewires cool, they become set to the new configuration. If the wires arelater disfigured, they will return to the set configuration upon heatingor simply releasing the wires. The force with which a super-elastic orshape memory alloy returns to a set configuration can be increased bymodifying the temperature at which the configuration is set, or bymodifying the period of time the alloy is maintained at the elevatedsetting temperature. For example, good results have been attainedsetting a Nitinol support structure of the present invention at 530° C.for 7 minutes. Stiffer support structures can be made using the sameNitinol wire by setting the structure at a temperature other than 530°C. or by setting the structure at 530° C. for a time other than 7minutes, or both.

The device 100 includes a wireform 104, to which a valve 106 isattached. The wireform 104 form commissural points 109 separated byarcuate portions 110. The arcuate portions 110 are attached to an insidesurface of the support structure 102. The commissural points 109facilitate natural and efficient opening and closing of the valve 106.Alternatively, the valve commissural points can be attached to an outersurface of the support structure (not shown).

The valve 106 may be any form of prosthetic or harvested biologicalvalve. Preferably, as shown in the Figures, the valve 106 is a valvehaving three leaflets. The valve 106 is sutured or otherwise attached tothe wireform 104. Preferably, the valve 106 is cut or constructed toinclude a skirt portion 112 which continues along the length of thesupport structure 102 in its deployed configuration.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

1. A stentless support structure comprising: at least one strand braidedto form a tubular structure having a first configuration and a secondconfiguration; whereby in the first configuration, the tubular structureincludes: a first end and a second end; an elongate body between thefirst end and the second end; whereby in the second configuration, thetubular structure includes at least one fold creating a section of thebody having more than one ply.
 2. The stentless support structure ofclaim 1 wherein said at least one fold shortens the body longitudinallyin the second configuration.
 3. The stentless support structure of claim1 wherein said tubular structure comprises a single ply in the firstconfiguration.
 4. The stentless support structure of claim 1 whereinsaid tubular structure comprises a multi-ply section in the secondconfiguration.
 5. The stentless support structure of claim 1 whereby, inthe first configuration, said stentless support structure is capable ofbeing housed with a lumen of a 20 Fr catheter.
 6. The stentless supportstructure of claim 1 wherein said first end comprises an unbraided end.7. The stentless support structure of claim 1 wherein said second endcomprises a folded end.
 8. The stentless support structure of claim 1wherein said first end comprises a plurality of commissural attachmentpoints.
 9. The stentless support structure of claim 1 wherein said firstend comprises a plurality of unbraided strands combined to form at leastone commissural attachment point.
 10. The stentless support structure ofclaim 1 wherein said plurality of strands braided together to form atubular structure comprises a plurality of strands of a first diameterand at least one fiber of a second diameter larger than the firstdiameter.
 11. The stentless support structure of claim 1 wherein saidfirst end comprises a wire form having a plurality of commissuralattachment points.
 12. The stentless support structure of claim 1further comprising a lining in an inner wall of the tubular structure.13. The stentless support structure of claim 4 further comprising alining sandwiched between said first and second ply.
 14. A method ofimplanting a support structure comprising: (a) percutaneously deliveringa support structure in an elongated state inside a catheter to a targetsite; (b) retracting said catheter relative to said support structuresuch that a first portion of said support structure expands againstnative tissue of the target site; (c) advancing a second portion of saidsupport structure into said first portion such that a first fold iscreated between said first and second portions; (d) retracting saidcatheter relative to said second portion until said second portionexpands against an interior of said first portion, thereby creating amulti-layered support structure; (e) repeating steps (c) and (d) ifadditional layers are desired; (f) releasing the support structure andremoving said catheter from the target site.
 15. The method of claim 14wherein step (b) comprises retracting said catheter relative to saidsupport structure such that a first portion of said support structureexpands against native tissue of the target site, said first portionincluding a distal end and a proximal end, the distal end including acuff.
 16. The method of claim 15 wherein step (b) comprises: retractingsaid catheter relative to said support structure until said cuff expandsand contacts the native tissue of the target site; pulling said cuff ina proximal direction until the cuff contacts a distal side of a nativevalve; retracting said catheter relative to said support structure untilsaid proximal side of said first portion expands and contacts the nativetissue of the target site.
 17. A method of supporting native tissue of atarget site comprising: introducing material into the target sitelacking sufficient structural integrity to support the native tissue;building a supporting structure using said material in situ.
 18. Themethod of claim 17 wherein introducing material into the target sitelacking sufficient structural integrity to support the native tissuecomprises introducing a braided, elongate mesh tube.
 19. The method ofclaim 18 wherein introducing a braided, elongate mesh tube comprisesintroducing a braided, elongate mesh tube of at least one strand of amaterial selected from the group consisting of super-elastic and shapememory.
 20. The method of claim 19 wherein introducing a braided,elongate mesh tube of at least one strand of a material selected fromthe group consisting of super-elastic and shape memory comprisesintroducing a braided, elongate mesh tube of a single Nitinol strandhaving been preformed to a folded configuration.
 21. The method of claim17 wherein building a supporting structure using said material in situcomprises folding said material upon itself until sufficient structuralintegrity to support the native tissue is attained.
 22. The method ofclaim 21 wherein folding said material upon itself until sufficientstructural integrity to support the native tissue is attained comprises:introducing a delivery catheter to the target site containing saidmaterial in an elongated form; exposing a first length of said material,thereby allowing said first length of material to expand; advancing asecond length of said material inside said first length; exposing saidsecond length of said material, thereby allowing said second length toexpand against an inside surface of said first length.
 23. The method ofclaim 22 further comprising: advancing a third length of said materialinside said second length; exposing said third length of said material,thereby allowing said third length to expand against an inside surfaceof said second length.
 24. A stentless support structure comprising: astrand braided to form a tubular structure having a first configurationand a second configuration; whereby in the first configuration, thetubular structure includes: a first end and a second end; an elongatetubular body between the first end and the second end; whereby in thesecond configuration, the tubular structure includes: at least one foldshortening the body and creating a section of the body having at leasttwice as many ply as the elongate body in the extended configuration.25. A method of implanting a support structure comprising: (a)percutaneously delivering a support structure in an elongated stateinside a catheter to a target site; (b) retracting said catheterrelative to said support structure such that a first portion of saidsupport structure expands outside of said catheter; (c) advancing asecond portion of said support structure into said first portion suchthat a first fold is created between said first and second portions; (d)retracting said catheter relative to said second portion until saidsecond portion expands against an interior of said first portion,thereby creating a multi-layered support structure; (e) repeating steps(c) and (d) if additional layers are desired; (f) releasing the supportstructure and removing said catheter from the target site.
 26. Themethod of claim 25 wherein step (b) comprises retracting said catheterrelative to said support structure such that a first portion of saidsupport structure expands against native tissue of the target site, saidfirst portion including a distal end and a proximal end, the distal endincluding a cuff.
 27. The method of claim 26 wherein step (b) comprises:retracting said catheter relative to said support structure until saidcuff expands and contacts the native tissue of the target site; pullingsaid cuff in a proximal direction until the cuff contacts a distal sideof a native orifice; retracting said catheter relative to said supportstructure until said proximal side of said first portion expands andcontacts the native tissue of the target site.
 28. The method of claim25 wherein retracting said catheter relative to said support structuresuch that a first portion of said support structure expands outside ofsaid catheter comprises retracting said catheter relative to saidsupport structure such that a first portion of said support structureexpands outside of said catheter against native tissue of the targetsite.
 29. The method of claim 25 wherein step (b) comprises retractingsaid catheter relative to said support structure such that a firstportion of said support structure expands against native tissuebelonging to the group consisting of valve tissue, blood vessel tissue,and heart tissue.